Random things are considered hysterically funny by some, while others find random things extremely pointless.
Bob: Why Rob!?!! OMFG
Rob: *insert punchline here*
Bob: OMFG, n00b, I heard that before, it's not funny *punches Rob*
(This example is a perfect example. Not because Rob is trying to be funny, but because I made it trying to be funny, but it failed miserably.)